Well you'd be adding a charge and hopefully mitigating the addiction, which is a rational tradeoff. And this is assuming this person doesn't already have a record.
Except I believe the person is better off with a record than continuing to do meth. You'd turn your back as the baby drowns in the tub. You might even open the faucet before doing so.
Portugal is not tightening it down based on data, but based on perceptions. A shift to populism reverting previous progressive changes proves nothing.
Also, we didn't experiment with permissiveness, we fixed a heroin crisis that was completely out of control. You have no idea how bad it got before we stopped throwing addicts in jail and started providing them with rehab.